Fine scale structure of convective mixed layer in ice-covered lake
Fine scale structure of convective mixed layer in ice-covered lake
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DOI：
10.1007/s10652-018-9652-2
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发表时间：
2018-12
影响因子：
2.2
通讯作者：
S. Volkov;S. Bogdanov;R. Zdorovennov;G. Zdorovennova;A. Terzhevik;N. Palshin;D. Bouffard;G. Kirillin
中科院分区：
文献类型：
--
作者：
S. Volkov;S. Bogdanov;R. Zdorovennov;G. Zdorovennova;A. Terzhevik;N. Palshin;D. Bouffard;G. Kirillin
分布浮力源强迫的非定常对流是一种基本的环境流体力学过程，尤其是在覆冰淡水水体中。在这篇文章中，我们给出了新的基于场的结果，该结果表征了冰盖湖泊中辐射驱动对流的主要能量的日演变，即辐射诱导的浮力通量B和动能耗散率。为了估计湍流的时空分布，我们利用速度结构函数的尺度相似性从高频速度测量中识别出细小的湍流尺度。这项实地研究于2016年4月在俄罗斯文德尤尔斯科湖进行。利用声学多普勒海流剖面仪测量了冰盖下2m层的小尺度流速起伏。该方法对无平均切变的低能对流是有效的。通过对结构函数法拟合幂定律，确定了空间域覆盖数量级的惯性子范围，从而确定了湍流充分发展的区域。计算的湍动能耗散率可达。虽然观察到与B之间有很强的相关性，但在加热期开始后约1小时才开始回升。这一延迟大致相当于包含涡流的能量的周转时间。在松弛阶段，我们终于在夜间观察到了一次衰变，但有趣的是，这个水平仍然高于统计误差。
Nonstationary convection forced by distributed buoyancy sources is a fundamental environmental fluid mechanics process, particularly in ice-covered freshwater waterbodies. In this paper, we present novel field-based results that characterise the diurnal evolution of the main energetics of radiatively-driven convection in ice-covered lakes that is the radiatively-induced buoyancy flux, B, and the kinetic energy dissipation rate,. To estimate the spatiotemporal distribution of, we applied scale similarity of the velocity structure functions to identify the fine turbulence scales from high-frequency velocity measurements. The field study was carried out at Lake Vendyurskoe, Russia, in April 2016. Small-scale velocity fluctuations were measured using acoustic Doppler current profiler in a 2 m layer beneath the ice cover. The method was proven to be valid for low-energy convection without mean shear. The inertial subrange, covering order of magnitude in the spatial domain, was identified by fitting thescaling power law to the structure function method, thus confirming the regime of fully developed turbulence. The calculated rate of dissipation of turbulent kinetic energyreaches values up to. Although a strong correlation betweenand B was observed,picks up about 1 h later after the onset of the heating-phase. This delay roughly corresponds to the turnover time of the energy containing eddies. We finally observed a decay ofat night, during the relaxation-phase, but, interestingly, the level remained above the statistical error.